Eutrophication is a serious water quality issue that occurs due to the excess nutrient loads entering the water bodies. Esteghlal Dam is the source of supplying 50% of the drinking water of Bandar Abbas, which has been affected by algal blooms due to the excess nutrient loads from the Minab basin. The purpose of this study is to identify Critical Source Areas (CSAs) and study and prioritize management scenarios to reduce pollution load to the reservoir. In this study, we used an integrated quantitative and qualitative simulation approach at the basin scale. We applied the SWAT model as a comprehensive process-oriented model to simulate the entire watershed. After identifying CSAs, we assessed the impact of each management scenario on reducing the nutrients. Finally, based on the nutrient load reduction and the investment and operating costs of each scenario, we select appropriate solutions using a multi-criteria decision-making approach. The results showed that agricultural and pastures (livestock) land uses in Jaghin and Minab sub-basins are CSAs. In addition, Filter Strip with a width of at least 10 meters and Fertilizer Reduction on Farms were recognized as the most effective strategies.